{"id":55726,"date":"2026-06-12T10:32:37","date_gmt":"2026-06-12T10:32:37","guid":{"rendered":"https:\/\/xtmim.com\/?p=55726"},"modified":"2026-06-12T10:32:40","modified_gmt":"2026-06-12T10:32:40","slug":"critical-dimensions-before-switching-cnc-to-mim","status":"publish","type":"post","link":"https:\/\/xtmim.com\/ja\/blogs\/critical-dimensions-before-switching-cnc-to-mim\/","title":{"rendered":"CNC\u90e8\u54c1\u304b\u3089MIM\u3078\u306e\u5207\u308a\u66ff\u3048\u306b\u304a\u3051\u308b\u91cd\u8981\u5bf8\u6cd5"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"55726\" class=\"elementor elementor-55726\" data-elementor-post-type=\"post\">\n\t\t\t\t<div class=\"elementor-element elementor-element-93978e9 e-flex e-con-boxed cmsmasters-block-default e-con e-parent\" data-id=\"93978e9\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-b098962 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class=\"xtmim-cnc-critical-dimensions\">\r\n  <header class=\"xtmim-hero\">\r\n    <div class=\"xtmim-container xtmim-hero-content\">\r\n      <p class=\"xtmim-eyebrow\">CNC-to-MIM drawing review<\/p>\r\n      <h2>How to Review Critical Dimensions Before Switching From CNC to MIM<\/h2>\r\n      <p class=\"xtmim-hero-lede\">\r\n        Before switching a CNC-machined part to metal injection molding, the project team should not review every drawing dimension with the same priority. The first step is to separate functional dimensions, datum surfaces, mating features, sealing or sliding interfaces, and inspection-critical dimensions from general profile or cosmetic dimensions. This matters because MIM tooling, sintering shrinkage, possible sizing, selective machining, and production inspection all depend on which dimensions actually control function.\r\n      <\/p>\r\n\r\n      <div class=\"xtmim-quick-answer\">\r\n        <p>\r\n          <strong>Quick answer:<\/strong> CNC drawing dimensions should be reviewed by function before MIM tooling begins. Identify which dimensions control assembly, motion, sealing, alignment, inspection, or downstream operations. Then decide which features can remain as-sintered, which may need tooling compensation, and which may require MIM sizing or post-sintering machining.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <div class=\"xtmim-btn-row\">\r\n        <a class=\"xtmim-btn xtmim-btn-primary\" href=\"https:\/\/xtmim.com\/submit-drawing-for-review\/\">Submit Drawing for Review<\/a>\r\n        <a class=\"xtmim-btn xtmim-btn-secondary\" href=\"https:\/\/xtmim.com\/mim-comparison\/mim-vs-cnc\/\">Compare MIM vs CNC Machining<\/a>\r\n      <\/div>\r\n\r\n      <figure class=\"xtmim-figure xtmim-hero-figure xtmim-image-frame\" data-image-status=\"final\" data-image-slot=\"image-01-hero\">\r\n        <img fetchpriority=\"high\" src=\"https:\/\/xtmim.com\/wp-content\/uploads\/2026\/06\/01-cnc-to-mim-critical-dimension-review-hero-1.webp\" alt=\"Engineering review desk with CNC drawing, caliper, and small MIM-style metal components for checking critical dimensions before switching to metal injection molding.\" width=\"2172\" height=\"724\" loading=\"eager\" fetchpriority=\"high\" decoding=\"async\">\r\n        <figcaption>Critical dimensions should be reviewed by function before a CNC-machined part is moved to MIM tooling.<\/figcaption>\r\n        <p class=\"xtmim-figure-note\"><strong>Core conclusion:<\/strong> CNC drawing dimensions must be separated into functional, datum, assembly, and inspection-critical features before MIM tooling review.<\/p>\r\n      <\/figure>\r\n    <\/div>\r\n  <\/header>\r\n\r\n  <section class=\"xtmim-section\">\r\n    <div class=\"xtmim-container xtmim-reading\">\r\n      <h2>Quick Answer: Which Dimensions Need Review Before Moving From CNC to MIM?<\/h2>\r\n      <p>\r\n        The dimensions that need the most attention are not always the tightest numbers on the drawing. In a CNC-to-MIM review, a dimension becomes critical when it affects assembly, motion, sealing, alignment, load transfer, inspection, or a downstream process. A loose-looking dimension may be critical if it controls function, while a tight tolerance may be less important if it only reflects the original CNC machining setup.\r\n      <\/p>\r\n      <p>\r\n        Typical critical dimensions include hole position and hole diameter for pins, shafts, screws, or alignment features; datum surfaces used for assembly or inspection; flat faces that control seating, stack-up, or orientation; sliding, rotating, or wear-contact surfaces; sealing faces, grooves, or interfaces; threaded features and functional holes; thin walls, slots, undercuts, and small features that may be affected by molding or sintering; and dimensions tied to CMM, gauge, or functional inspection.\r\n      <\/p>\r\n      <div class=\"xtmim-callout\">\r\n        <p class=\"xtmim-callout-title\">Review principle<\/p>\r\n        <p>\r\n          From a design review perspective, the supplier should understand why each critical dimension matters. A tight dimension without functional context may lead to unnecessary cost. A functional dimension hidden inside a general tolerance block may create tooling risk, inspection disputes, or late-stage correction work.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <div class=\"xtmim-grid xtmim-grid-3\">\r\n        <div class=\"xtmim-card xtmim-card-soft\">\r\n          <h3>Function risk<\/h3>\r\n          <p>\r\n            If a mating hole, sliding surface, or sealing face is not identified as critical, the MIM route may be quoted without the right secondary operation or inspection plan.\r\n          <\/p>\r\n        <\/div>\r\n        <div class=\"xtmim-card xtmim-card-soft\">\r\n          <h3>Tooling risk<\/h3>\r\n          <p>\r\n            If the tooling team does not know which dimensions must be protected, shrinkage compensation and feature design may be reviewed too generally.\r\n          <\/p>\r\n        <\/div>\r\n        <div class=\"xtmim-card xtmim-card-soft\">\r\n          <h3>Inspection risk<\/h3>\r\n          <p>\r\n            If datum and measurement methods are not agreed before tooling, sample approval and production inspection can become inconsistent.\r\n          <\/p>\r\n        <\/div>\r\n      <\/div>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section class=\"xtmim-section xtmim-section-tight\">\r\n    <div class=\"xtmim-container xtmim-reading\">\r\n      <h2>Why CNC Drawing Dimensions Cannot Be Copied Directly Into MIM Tooling Review<\/h2>\r\n      <p>\r\n        A CNC drawing often reflects the way the part was originally machined. Some dimensions may be tight because they were easy to control on a CNC setup, not because the product function truly requires that level of control. When the same part is considered for MIM, the manufacturing logic changes.\r\n      <\/p>\r\n      <p>\r\n        CNC machining removes material from bar stock, plate, casting, or a machined blank. The part is dimensionally stable during most of the process, and critical surfaces can often be finished directly with cutting tools. MIM is different. The part is shaped in a mold, handled as a green part, debound, and sintered. During sintering, the part shrinks. The tooling must compensate for this shrinkage, and the final dimensional result depends on geometry, material, support, sintering behavior, and inspection strategy.\r\n      <\/p>\r\n      <p>\r\n        This does not mean MIM cannot control critical features. It means the review must ask a different question: which dimensions should be controlled by the mold and sintering process, and which dimensions should be protected by design adjustment, sizing, machining, fixture control, or functional inspection?\r\n      <\/p>\r\n      <p>\r\n        A common mistake is to send a CNC drawing to a MIM supplier and ask whether the same tolerances can be achieved without explaining which dimensions are functional. That approach can lead to either over-conservative pricing or under-reviewed tooling risk. For the broader process selection context, the parent <a href=\"https:\/\/xtmim.com\/mim-comparison\/mim-vs-cnc\/\">MIM vs CNC machining comparison<\/a> should be reviewed together with this drawing-level checklist.\r\n      <\/p>\r\n      <p>\r\n        If the drawing is close to tooling discussion, the same review should also be connected with a broader <a href=\"https:\/\/xtmim.com\/blogs\/mim-design-review-before-tooling\/\">MIM design review before tooling<\/a> so that geometry, tolerance intent, material expectations, and inspection planning are checked before mold investment.\r\n      <\/p>\r\n      <div class=\"xtmim-callout\">\r\n        <p class=\"xtmim-callout-title\">Engineering review question<\/p>\r\n        <p>\r\n          The practical review question is not \u201cCan MIM match CNC?\u201d The better question is \u201cWhich dimensions must be controlled by molding and sintering, which can be relaxed because they are non-functional, and which must be reserved for sizing, machining, finishing, or functional inspection?\u201d This keeps the discussion tied to cost, tooling risk, and production approval instead of a generic process comparison.\r\n        <\/p>\r\n      <\/div>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section class=\"xtmim-section\">\r\n    <div class=\"xtmim-container\">\r\n      <div class=\"xtmim-reading\">\r\n        <h2>Classify Critical Dimensions by Function Before the Supplier Review<\/h2>\r\n        <p class=\"xtmim-section-intro\">\r\n          Before the supplier reviews tooling feasibility, the engineering team should classify drawing dimensions by function. This helps separate necessary control points from dimensions that are less important to product performance. It also helps the supplier quote the project with the correct manufacturing route instead of assuming that every CNC tolerance must be reproduced exactly.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <div class=\"xtmim-grid xtmim-grid-2\">\r\n        <div class=\"xtmim-card\">\r\n          <h3>Functional fit dimensions<\/h3>\r\n          <p>\r\n            These dimensions control whether the part assembles correctly with another component. Examples include pin holes, shaft seats, snap areas, slot width, screw clearance, and location features. If a functional fit dimension is wrong, the part may fail assembly even if the rest of the geometry looks acceptable.\r\n          <\/p>\r\n          <p>\r\n            For MIM review, these dimensions should be clearly marked on the drawing. The supplier should know whether the dimension controls clearance, interference, alignment, rotation, or load transfer.\r\n          <\/p>\r\n        <\/div>\r\n\r\n        <div class=\"xtmim-card\">\r\n          <h3>Datum and locating surfaces<\/h3>\r\n          <p>\r\n            Datum surfaces are often more important than the tolerance value itself. A dimension may look reasonable on paper, but if the datum structure is unclear, inspection and production control become unstable.\r\n          <\/p>\r\n          <p>\r\n            Before tooling, confirm which faces or features will be used for inspection, assembly orientation, and fixture location. If a CNC part used a machined flat as a datum, the MIM version may need the same surface protected, redesigned, sized, or selectively machined.\r\n          <\/p>\r\n        <\/div>\r\n\r\n        <div class=\"xtmim-card\">\r\n          <h3>Thread, hole, slot, and pin features<\/h3>\r\n          <p>\r\n            Holes, slots, and threads need separate review because their risk depends on diameter, depth, wall thickness, location, molding direction, and whether the feature is molded, drilled, tapped, reamed, or finished after sintering.\r\n          <\/p>\r\n          <p>\r\n            Not every hole should be machined after MIM. However, precision holes, deep small holes, tight pin locations, and thread features may need a defined manufacturing route before the quote is finalized.\r\n          <\/p>\r\n        <\/div>\r\n\r\n        <div class=\"xtmim-card\">\r\n          <h3>Sealing, sliding, and wear-contact surfaces<\/h3>\r\n          <p>\r\n            Sealing faces and sliding surfaces should not be treated as ordinary cosmetic surfaces. Even if the drawing tolerance is not extremely tight, the surface may be function-critical. The review should confirm flatness, surface finish expectations, contact pressure, mating material, and whether the surface must be finished after sintering.\r\n          <\/p>\r\n        <\/div>\r\n      <\/div>\r\n\r\n      <div class=\"xtmim-table-wrap\" role=\"region\" aria-label=\"Critical dimension classification table\">\r\n        <table>\r\n          <thead>\r\n            <tr>\r\n              <th>Dimension Type<\/th>\r\n              <th>Why It Matters<\/th>\r\n              <th>CNC-to-MIM Review Question<\/th>\r\n              <th>Possible MIM Route<\/th>\r\n            <\/tr>\r\n          <\/thead>\r\n          <tbody>\r\n            <tr>\r\n              <td>Functional fit dimension<\/td>\r\n              <td>Controls assembly or movement<\/td>\r\n              <td>What does this dimension mate with?<\/td>\r\n              <td>Molded, sized, or selectively machined<\/td>\r\n            <\/tr>\r\n            <tr>\r\n              <td>Datum surface<\/td>\r\n              <td>Controls inspection and location<\/td>\r\n              <td>Is this the real production datum?<\/td>\r\n              <td>Protected by tooling, fixture, sizing, or machining<\/td>\r\n            <\/tr>\r\n            <tr>\r\n              <td>Precision hole or slot<\/td>\r\n              <td>Controls pin, screw, or alignment<\/td>\r\n              <td>Is the hole molded, drilled, reamed, or tapped?<\/td>\r\n              <td>Molded feature plus possible secondary operation<\/td>\r\n            <\/tr>\r\n            <tr>\r\n              <td>Sealing or sliding surface<\/td>\r\n              <td>Controls leakage, motion, or wear<\/td>\r\n              <td>What surface finish and flatness are required?<\/td>\r\n              <td>As-sintered if acceptable, or finished after sintering<\/td>\r\n            <\/tr>\r\n            <tr>\r\n              <td>Cosmetic profile<\/td>\r\n              <td>Affects appearance more than function<\/td>\r\n              <td>Does this tolerance affect performance?<\/td>\r\n              <td>Often controlled by normal MIM process capability<\/td>\r\n            <\/tr>\r\n            <tr>\r\n              <td>General tolerance dimension<\/td>\r\n              <td>Supports drawing completeness<\/td>\r\n              <td>Is this actually critical or only inherited from CNC?<\/td>\r\n              <td>Reviewed case by case<\/td>\r\n            <\/tr>\r\n          <\/tbody>\r\n        <\/table>\r\n      <\/div>\r\n\r\n      <p class=\"xtmim-muted\">\r\n        Use this table as a review filter, not as a replacement for a full DFM review. The supplier still needs the 3D model, 2D drawing, material expectation, annual volume, and functional explanation before confirming whether a feature should be molded, sized, machined, or redesigned. For more background on why geometry and dimensions affect the final sintered result, review <a href=\"https:\/\/xtmim.com\/blogs\/how-part-dimensions-affect-final-mim-part-quality\/\">how part dimensions affect final MIM part quality<\/a>.\r\n      <\/p>\r\n\r\n      <figure class=\"xtmim-figure xtmim-image-frame\" data-image-status=\"final\" data-image-slot=\"image-02-dimension-categories\">\r\n        <img loading=\"lazy\" src=\"https:\/\/xtmim.com\/wp-content\/uploads\/2026\/06\/02-critical-dimension-categories-mim-review-1.webp\" alt=\"Small MIM-style metal component with light labels showing fit, datum, hole, and surface areas for critical dimension review.\" width=\"1600\" height=\"900\" loading=\"lazy\" decoding=\"async\">\r\n        <figcaption>Critical dimensions should be classified by function before the supplier evaluates MIM tooling feasibility.<\/figcaption>\r\n        <p class=\"xtmim-figure-note\"><strong>Core conclusion:<\/strong> Function-based dimension classification helps separate true critical features from inherited CNC drawing tolerances.<\/p>\r\n      <\/figure>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section class=\"xtmim-section xtmim-section-tight\">\r\n    <div class=\"xtmim-container\">\r\n      <div class=\"xtmim-reading\">\r\n        <h2>Identify Dimensions That May Need Sizing or Post-Sintering Machining<\/h2>\r\n        <p>\r\n          Some CNC dimensions can be converted to MIM without secondary machining. Others may need selective correction after sintering. The key is to avoid two extremes: assuming MIM can hold every CNC dimension directly, or assuming every precision feature must be machined again.\r\n        <\/p>\r\n        <p>\r\n          A stronger review approach is feature-by-feature route planning. For each critical feature, the project team should define the required function, likely MIM control method, possible secondary operation, inspection method, and cost impact before tooling starts.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <div class=\"xtmim-grid xtmim-grid-2\">\r\n        <div class=\"xtmim-card xtmim-card-soft\">\r\n          <h3>Precision bores and bearing seats<\/h3>\r\n          <p>\r\n            Bores that carry shafts, pins, bearings, or rotating elements should be reviewed carefully. The supplier should know whether the bore controls free movement, press fit, concentricity, or alignment. Depending on size and function, the route may involve molding, sizing, reaming, or other post-sintering correction.\r\n          <\/p>\r\n        <\/div>\r\n\r\n        <div class=\"xtmim-card xtmim-card-soft\">\r\n          <h3>Flat datum surfaces<\/h3>\r\n          <p>\r\n            A flat datum surface may be simple in CNC machining but more sensitive in MIM if the part shape, wall thickness, or sintering support allows distortion. If the flatness controls assembly, inspection, or stack-up, the review should confirm whether the datum can remain as-sintered or requires correction.\r\n          <\/p>\r\n        <\/div>\r\n\r\n        <div class=\"xtmim-card xtmim-card-soft\">\r\n          <h3>Threads and functional holes<\/h3>\r\n          <p>\r\n            Threaded features need a manufacturing decision before quotation. Some features may be molded as pilot holes and tapped later. Others may be redesigned for inserts, clearance holes, or a different fastening method. The decision depends on strength, tolerance, material, production volume, and assembly function.\r\n          <\/p>\r\n        <\/div>\r\n\r\n        <div class=\"xtmim-card xtmim-card-soft\">\r\n          <h3>Sealing faces and sliding surfaces<\/h3>\r\n          <p>\r\n            Sealing and sliding surfaces often need more than dimensional review. Surface condition, contact area, wear behavior, and mating geometry should be confirmed. If a surface is both dimension-critical and finish-critical, it may require a controlled finishing operation after sintering.\r\n          <\/p>\r\n        <\/div>\r\n      <\/div>\r\n\r\n      <div class=\"xtmim-table-wrap\" role=\"region\" aria-label=\"Sizing and machining decision matrix\">\r\n        <table>\r\n          <thead>\r\n            <tr>\r\n              <th>Feature<\/th>\r\n              <th>As-Sintered MIM May Be Acceptable When<\/th>\r\n              <th>Sizing May Be Needed When<\/th>\r\n              <th>Post-Sintering Machining May Be Needed When<\/th>\r\n            <\/tr>\r\n          <\/thead>\r\n          <tbody>\r\n            <tr>\r\n              <td>General outer profile<\/td>\r\n              <td>It is not a datum or mating feature<\/td>\r\n              <td>Local correction improves repeatability<\/td>\r\n              <td>Tight profile must match a functional interface<\/td>\r\n            <\/tr>\r\n            <tr>\r\n              <td>Pin hole<\/td>\r\n              <td>Clearance is generous and function is not sensitive<\/td>\r\n              <td>Location or diameter needs correction<\/td>\r\n              <td>Tight fit, reaming, or threaded function is required<\/td>\r\n            <\/tr>\r\n            <tr>\r\n              <td>Flat datum<\/td>\r\n              <td>Datum function is low-risk<\/td>\r\n              <td>Controlled seating surface is needed<\/td>\r\n              <td>High flatness or precise reference surface is required<\/td>\r\n            <\/tr>\r\n            <tr>\r\n              <td>Thread area<\/td>\r\n              <td>Thread is not required or design is changed<\/td>\r\n              <td>Geometry needs local correction<\/td>\r\n              <td>Tapping, drilling, or precise thread control is required<\/td>\r\n            <\/tr>\r\n            <tr>\r\n              <td>Sealing face<\/td>\r\n              <td>Surface finish is not function-critical<\/td>\r\n              <td>Local contact improvement is enough<\/td>\r\n              <td>Sealing performance requires finishing<\/td>\r\n            <\/tr>\r\n          <\/tbody>\r\n        <\/table>\r\n      <\/div>\r\n\r\n      <div class=\"xtmim-callout\">\r\n        <p class=\"xtmim-callout-title\">Supplier confirmation before tooling<\/p>\r\n        <p>\r\n          Before mold manufacturing begins, ask the supplier to confirm which critical dimensions are expected to be controlled as-sintered, which may require sizing, which require post-sintering machining, and which should be redesigned to reduce tooling risk. This helps avoid late sample-stage disputes about whether a secondary operation was included in the original quote.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <p class=\"xtmim-muted\">\r\n        This matrix should be reviewed before tooling, not after the first samples fail inspection. Late decisions often add cost, extend lead time, and create disagreement about whether a feature was included in the original quote. For process-specific follow-up, review <a href=\"https:\/\/xtmim.com\/mim-process\/secondary-operations\/mim-sizing\/\">MIM sizing<\/a> and <a href=\"https:\/\/xtmim.com\/mim-process\/secondary-operations\/post-sintering-machining\/\">post-sintering machining<\/a> as separate routes rather than assuming every feature needs CNC finishing.\r\n      <\/p>\r\n\r\n      <figure class=\"xtmim-figure xtmim-image-frame\" data-image-status=\"final\" data-image-slot=\"image-03-sizing-machining-review\">\r\n        <img loading=\"lazy\" src=\"https:\/\/xtmim.com\/wp-content\/uploads\/2026\/06\/03-sizing-machining-review-critical-mim-features-1.webp\" alt=\"Small MIM-style metal part showing bore, flat face, thread area, and contact surface that may need sizing or post-sintering machining review.\" width=\"1600\" height=\"900\" loading=\"lazy\" decoding=\"async\">\r\n        <figcaption>Some critical dimensions may remain as-sintered, while others require sizing or selective post-sintering machining.<\/figcaption>\r\n        <p class=\"xtmim-figure-note\"><strong>Core conclusion:<\/strong> Secondary operations should be planned only for features whose function requires tighter control than the as-sintered route can provide.<\/p>\r\n      <\/figure>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section class=\"xtmim-section\">\r\n    <div class=\"xtmim-container\">\r\n      <div class=\"xtmim-reading\">\r\n        <h2>Review Tolerances Together With Datum Strategy and Inspection Method<\/h2>\r\n        <p>\r\n          A tolerance is only useful if the datum and inspection method are clear. When a CNC part is converted to MIM, the inspection plan may need to change because the feature formation method changes. This is especially important when the CNC prototype was inspected using machining setup references that will not exist in the same way during MIM production.\r\n        <\/p>\r\n\r\n        <h3>Confirm the real datum structure<\/h3>\r\n        <p>\r\n          The drawing may show formal datums, but the actual CNC process may have relied on machining setup surfaces that are not clearly defined for MIM production. Before tooling, confirm which surfaces control assembly and which surfaces control inspection. If a datum is critical, the supplier should know whether it must remain as-sintered, be sized, or be machined.\r\n        <\/p>\r\n\r\n        <h3>Separate production inspection from prototype inspection<\/h3>\r\n        <p>\r\n          A CNC prototype may have been checked with manual tools, one-off fixtures, or CMM programs built around the CNC process. MIM production requires repeatable inspection logic. The team should define which dimensions need routine production inspection and which dimensions only require sample or validation-stage confirmation.\r\n        <\/p>\r\n\r\n        <h3>Define CMM, gauge, or functional inspection needs<\/h3>\r\n        <p>\r\n          Some dimensions are best inspected by CMM. Others may be more meaningful through functional gauges or assembly checks. For example, a pin alignment feature may require positional inspection, while a sliding interface may need a functional movement check. If the inspection method is not agreed before tooling, the team may approve a drawing tolerance that is difficult to measure consistently in production.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <div class=\"xtmim-card\">\r\n        <h3>Datum + Inspection Review Checklist<\/h3>\r\n        <ul class=\"xtmim-checklist\">\r\n          <li>Which surfaces are true functional datums?<\/li>\r\n          <li>Which dimensions control assembly fit, motion, sealing, or alignment?<\/li>\r\n          <li>Which dimensions are inherited from CNC but not function-critical?<\/li>\r\n          <li>Which tolerances are tied to CMM inspection?<\/li>\r\n          <li>Which features require functional gauges or assembly checks?<\/li>\r\n          <li>Which dimensions may need sizing, machining, or finishing after sintering?<\/li>\r\n          <li>Which dimensions are acceptable as normal MIM process-controlled dimensions?<\/li>\r\n          <li>Are surface finish and dimensional requirements separated clearly?<\/li>\r\n          <li>Are 2D drawing notes consistent with the 3D model?<\/li>\r\n          <li>Has the team marked critical-to-function dimensions before RFQ?<\/li>\r\n        <\/ul>\r\n      <\/div>\r\n\r\n      <div class=\"xtmim-callout\">\r\n        <p class=\"xtmim-callout-title\">Inspection dispute prevention<\/p>\r\n        <p>\r\n          If the datum, tolerance, and measurement method are reviewed separately, the project may pass design discussion but fail sample approval. A better review package connects each critical dimension to its inspection method: CMM for positional or profile control, gauge checks for repeatable production acceptance, and functional checks for movement, fit, sealing, or assembly behavior.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <figure class=\"xtmim-figure xtmim-image-frame\" data-image-status=\"final\" data-image-slot=\"image-04-datum-inspection\">\r\n        <img loading=\"lazy\" src=\"https:\/\/xtmim.com\/wp-content\/uploads\/2026\/06\/04-datum-inspection-review-mim-parts-1.webp\" alt=\"Inspection scene with small MIM-style metal component, fixture, gauge, and CMM-style probe for reviewing datum and critical dimensions.\" width=\"1600\" height=\"900\" loading=\"lazy\" decoding=\"async\">\r\n        <figcaption>A critical dimension is only useful when the datum structure and inspection method are clear.<\/figcaption>\r\n        <p class=\"xtmim-figure-note\"><strong>Core conclusion:<\/strong> CNC-to-MIM dimension review should connect tolerance, datum strategy, and repeatable inspection before tooling.<\/p>\r\n      <\/figure>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section class=\"xtmim-section xtmim-section-tight\">\r\n    <div class=\"xtmim-container\">\r\n      <div class=\"xtmim-reading\">\r\n        <h2>Composite Field Scenario for Engineering Training<\/h2>\r\n        <p>\r\n          A small CNC-machined locking component has several tight drawing dimensions, but only three are truly functional: a pin hole position, a flat locating face, and a sliding contact surface. Before moving the part to MIM, the supplier review should separate these critical dimensions from cosmetic edge radii and general profile dimensions.\r\n        <\/p>\r\n        <p>\r\n          The pin hole may require a tighter inspection plan. The locating face may need a clear datum strategy. The sliding surface may require post-sintering finishing or selective machining. At the same time, several outer profile dimensions may be acceptable under normal MIM process control if they do not affect assembly or motion.\r\n        <\/p>\r\n        <p>\r\n          This type of review helps the team avoid unnecessary cost while protecting the dimensions that actually determine part performance. It also supports the broader <a href=\"https:\/\/xtmim.com\/industry-solutions\/cnc-to-mim-conversion\/\">CNC to MIM conversion review<\/a> before tooling investment is made.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <div class=\"xtmim-grid xtmim-grid-3\">\r\n        <div class=\"xtmim-risk-item\">\r\n          <strong>Protected feature<\/strong>\r\n          The pin hole position should be marked as critical because it controls alignment and may require defined inspection.\r\n        <\/div>\r\n        <div class=\"xtmim-risk-item\">\r\n          <strong>Review feature<\/strong>\r\n          The flat locating face should be reviewed for datum stability and possible correction after sintering.\r\n        <\/div>\r\n        <div class=\"xtmim-risk-item\">\r\n          <strong>Flexible feature<\/strong>\r\n          Cosmetic radii and non-contact outer profiles may not need to keep CNC-level tolerance if they do not affect function.\r\n        <\/div>\r\n      <\/div>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section class=\"xtmim-section\">\r\n    <div class=\"xtmim-container\">\r\n      <div class=\"xtmim-reading\">\r\n        <h2>Critical Dimension Review Checklist Before Requesting a MIM Quote<\/h2>\r\n        <p>\r\n          A useful CNC-to-MIM RFQ should not only include a 3D model and a 2D drawing. It should also explain which dimensions matter and why they matter. A supplier can review moldability more effectively when the drawing separates functional requirements from inherited CNC machining habits.\r\n        <\/p>\r\n\r\n        <h3>What to mark on the 2D drawing<\/h3>\r\n        <ul class=\"xtmim-checklist\">\r\n          <li>Critical-to-function dimensions.<\/li>\r\n          <li>Assembly and mating dimensions.<\/li>\r\n          <li>Datum surfaces and locating features.<\/li>\r\n          <li>Tight holes, slots, threads, and pin locations.<\/li>\r\n          <li>Sealing, sliding, or wear-contact surfaces.<\/li>\r\n          <li>Surface finish requirements tied to function.<\/li>\r\n          <li>Dimensions that may affect inspection, gauge design, or acceptance criteria.<\/li>\r\n        <\/ul>\r\n\r\n        <h3>What to explain beyond the tolerance block<\/h3>\r\n        <p>\r\n          The title block tolerance does not explain product function. Add short notes for features that control fit, movement, sealing, load transfer, or assembly sequence. If a tolerance was copied from the CNC drawing but is not function-critical, clarify that it can be reviewed for MIM process capability. The <a href=\"https:\/\/xtmim.com\/mim-design-guide\/mim-tolerances\/\">MIM tolerance review<\/a> can support this discussion, but the actual project decision should be based on the part function.\r\n        <\/p>\r\n\r\n        <h3>What the supplier should confirm before tooling<\/h3>\r\n        <ul class=\"xtmim-checklist\">\r\n          <li>Which critical dimensions can be controlled as-sintered.<\/li>\r\n          <li>Which features may require tooling compensation.<\/li>\r\n          <li>Which dimensions may need sizing or machining.<\/li>\r\n          <li>Which surfaces require finishing.<\/li>\r\n          <li>Which inspection methods are practical for production.<\/li>\r\n          <li>Which drawing requirements may increase cost or lead time.<\/li>\r\n          <li>Which design changes may reduce risk before mold manufacturing.<\/li>\r\n          <li>Which assumptions should be confirmed before the tooling quote is finalized.<\/li>\r\n        <\/ul>\r\n      <\/div>\r\n\r\n      <figure class=\"xtmim-figure xtmim-image-frame\" data-image-status=\"final\" data-image-slot=\"image-05-rfq-input-package\">\r\n        <img loading=\"lazy\" src=\"https:\/\/xtmim.com\/wp-content\/uploads\/2026\/06\/05-drawing-package-cnc-to-mim-review-1.webp\" alt=\"Engineering input package with 2D drawing, 3D model reference, small MIM-style metal parts, and notes for CNC-to-MIM critical dimension review.\" width=\"1600\" height=\"900\" loading=\"lazy\" decoding=\"async\">\r\n        <figcaption>A useful MIM review package should include drawings, models, marked critical dimensions, and project requirements.<\/figcaption>\r\n        <p class=\"xtmim-figure-note\"><strong>Core conclusion:<\/strong> Better drawing inputs help the supplier review critical dimensions before tooling decisions are made.<\/p>\r\n      <\/figure>\r\n\r\n      <div class=\"xtmim-callout\">\r\n        <p class=\"xtmim-callout-title\">Before requesting a quote<\/p>\r\n        <p>\r\n          If the project is close to supplier review, prepare the 2D drawing, 3D model, annual volume target, material expectation, marked critical dimensions, and inspection notes. The <a href=\"https:\/\/xtmim.com\/resources\/project-checklists\/mim-tolerance-shrinkage-checklist\/\">tolerance and shrinkage checklist<\/a> and the <a href=\"https:\/\/xtmim.com\/rfq-preparation-guide\/\">MIM RFQ preparation guide<\/a> can help organize the input package.\r\n        <\/p>\r\n      <\/div>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section class=\"xtmim-section xtmim-section-tight\">\r\n    <div class=\"xtmim-container\">\r\n      <div class=\"xtmim-reading\">\r\n        <h2>When a CNC-to-MIM Dimension Review Should Stop the Project<\/h2>\r\n        <p>\r\n          A dimension review does not always lead directly to tooling. Sometimes it should stop the project until the design, tolerance strategy, or inspection plan is clarified.\r\n        <\/p>\r\n        <p>\r\n          The project should pause when critical dimensions depend on unrealistically tight as-sintered control, when functional surfaces are not clearly identified, or when the inspection method is not agreed before tooling. It should also pause when the part depends on CNC-only geometry that cannot be molded, supported, or sintered reliably without redesign.\r\n        <\/p>\r\n        <p>\r\n          Stopping the project at this stage is not a failure. It is a lower-cost correction point. Once tooling starts, changes to critical dimensions, datum strategy, or secondary operation routes can become much more expensive.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <div class=\"xtmim-decision-box\">\r\n        <div class=\"xtmim-card\">\r\n          <h3>Continue toward MIM tooling review when<\/h3>\r\n          <ul class=\"xtmim-checklist\">\r\n            <li>Critical dimensions are clearly marked.<\/li>\r\n            <li>Functional surfaces are separated from cosmetic dimensions.<\/li>\r\n            <li>Datum surfaces are agreed.<\/li>\r\n            <li>Inspection methods are practical.<\/li>\r\n            <li>Secondary operations are defined only where needed.<\/li>\r\n            <li>The 3D model and 2D drawing are consistent.<\/li>\r\n          <\/ul>\r\n        <\/div>\r\n\r\n        <div class=\"xtmim-card\">\r\n          <h3>Pause and review before tooling when<\/h3>\r\n          <ul class=\"xtmim-checklist\">\r\n            <li>Every CNC tolerance is treated as mandatory without function review.<\/li>\r\n            <li>Critical surfaces are not identified.<\/li>\r\n            <li>Tight holes, threads, or datums have no manufacturing route.<\/li>\r\n            <li>Inspection is unclear or not repeatable.<\/li>\r\n            <li>The design depends on CNC-only features.<\/li>\r\n            <li>Cost assumptions ignore sizing, machining, or finishing requirements.<\/li>\r\n          <\/ul>\r\n        <\/div>\r\n      <\/div>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section class=\"xtmim-section\">\r\n    <div class=\"xtmim-container xtmim-reading\">\r\n      <h2>FAQ About Reviewing Critical Dimensions Before CNC-to-MIM Conversion<\/h2>\r\n      <div class=\"xtmim-faq\">\r\n        <details>\r\n          <summary>Can CNC tolerances be kept when a part moves to MIM?<\/summary>\r\n          <p>Some CNC tolerances may be maintained through MIM tooling strategy, sizing, machining, or inspection control, but they should not be copied automatically. Each tight dimension should be reviewed based on function, geometry, material, production volume, and inspection method.<\/p>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>Which dimensions are usually most critical in a CNC-to-MIM review?<\/summary>\r\n          <p>The most critical dimensions usually include assembly fits, datum surfaces, precision holes, pin locations, sealing faces, sliding surfaces, thread areas, and dimensions tied to inspection or functional testing.<\/p>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>Does every tight dimension require post-sintering machining?<\/summary>\r\n          <p>No. Some tight or important dimensions can be controlled through MIM tooling and process control. Post-sintering machining should be used selectively for features that truly require tighter geometry, surface finish, or functional control than the as-sintered process can reasonably provide.<\/p>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>Should datum surfaces change when switching from CNC to MIM?<\/summary>\r\n          <p>They may need to be reviewed. A datum used in CNC machining may not be the best production datum for MIM. The team should confirm whether the datum is functional, measurable, and stable after sintering.<\/p>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>What should I mark on the drawing before asking for a MIM review?<\/summary>\r\n          <p>Mark functional dimensions, datum surfaces, mating features, precision holes, threads, sealing or sliding surfaces, surface finish requirements, and inspection-critical dimensions. Also explain annual volume, material expectation, and any required secondary operations.<\/p>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>Can a MIM supplier decide critical dimensions without functional context?<\/summary>\r\n          <p>A supplier can identify manufacturing risks, but the product team should explain which dimensions control function. Without functional context, the supplier may either over-control noncritical dimensions or miss a feature that is essential to assembly or performance.<\/p>\r\n        <\/details>\r\n      <\/div>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section class=\"xtmim-section xtmim-author\">\r\n    <div class=\"xtmim-container xtmim-reading\">\r\n      <div class=\"xtmim-card\">\r\n        <h2>Engineering Review Note<\/h2>\r\n        <p>\r\n          This article is written from a MIM drawing review and tooling preparation perspective. It is intended to help product engineers, sourcing teams, and project managers review CNC-machined part drawings before considering metal injection molding. The recommendations focus on dimension classification, functional risk, datum strategy, secondary operation planning, and RFQ preparation.\r\n        <\/p>\r\n        <p>\r\n          Final feasibility should always be confirmed through drawing review, material review, and supplier engineering discussion before tooling. XTMIM can review whether a CNC-machined part is suitable for MIM, which features may need additional control, and which drawing requirements should be clarified before mold investment.\r\n        <\/p>\r\n        <p>\r\n          This page is not a guaranteed tolerance commitment. Final dimensional feasibility depends on part geometry, material selection, tooling strategy, sintering behavior, secondary operation requirements, inspection method, and project-specific approval criteria.\r\n        <\/p>\r\n      <\/div>\r\n    <\/div>\r\n  <\/section>\r\n\r\n  <section class=\"xtmim-section\">\r\n    <div class=\"xtmim-container\">\r\n      <div class=\"xtmim-cta\">\r\n        <h2>Need a CNC-to-MIM Dimension Review Before Tooling?<\/h2>\r\n        <p>\r\n          Send your 2D drawing, 3D model, annual volume target, material expectation, and marked critical dimensions for engineering review. XTMIM can help identify which features may be suitable for as-sintered MIM, which may need sizing or post-sintering machining, and which drawing requirements should be clarified before tooling.\r\n        <\/p>\r\n        <div class=\"xtmim-btn-row\">\r\n          <a class=\"xtmim-btn xtmim-btn-primary\" href=\"https:\/\/xtmim.com\/submit-drawing-for-review\/\">Submit Drawing for Review<\/a>\r\n          <a class=\"xtmim-btn xtmim-btn-secondary\" href=\"https:\/\/xtmim.com\/contact-us\/\">Contact Engineering Team<\/a>\r\n        <\/div>\r\n      <\/div>\r\n    <\/div>\r\n  <\/section>\r\n<\/article>\r\n\r\n<script type=\"application\/ld+json\">\r\n{\r\n  \"@context\": \"https:\/\/schema.org\",\r\n  \"@graph\": [\r\n    {\r\n      \"@type\": \"TechArticle\",\r\n      \"@id\": \"https:\/\/xtmim.com\/blogs\/critical-dimensions-before-switching-cnc-to-mim\/#article\",\r\n      \"headline\": \"How to Review Critical Dimensions Before Switching From CNC to MIM\",\r\n      \"description\": 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Without functional context, the supplier may either over-control noncritical dimensions or miss a feature that is essential to assembly or performance.\"\r\n          }\r\n        }\r\n      ]\r\n    }\r\n  ]\r\n}\r\n<\/script>\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>CNC-to-MIM drawing review How to Review Critical Dimensions Before Switching From CNC to MIM Before switching a CNC-machined part to metal injection molding, the project team should not review every drawing dimension with the same priority. The first step is to separate functional dimensions, datum surfaces, mating features, sealing or sliding interfaces, and inspection-critical dimensions from general profile or cosmetic dimensions. This matters because MIM tooling, sintering shrinkage, possible sizing, selective machining, and production inspection all depend on which dimensions actually control function. Quick answer: CNC drawing dimensions should be reviewed by function before MIM tooling begins. Identify which dimensions control assembly, motion, sealing, alignment, inspection, or downstream operations. Then&#8230;<\/p>","protected":false},"author":1,"featured_media":55712,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[31],"tags":[],"class_list":["post-55726","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-mim-drawing-dfm-questions"],"_links":{"self":[{"href":"https:\/\/xtmim.com\/ja\/wp-json\/wp\/v2\/posts\/55726","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/xtmim.com\/ja\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/xtmim.com\/ja\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/xtmim.com\/ja\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/xtmim.com\/ja\/wp-json\/wp\/v2\/comments?post=55726"}],"version-history":[{"count":4,"href":"https:\/\/xtmim.com\/ja\/wp-json\/wp\/v2\/posts\/55726\/revisions"}],"predecessor-version":[{"id":55730,"href":"https:\/\/xtmim.com\/ja\/wp-json\/wp\/v2\/posts\/55726\/revisions\/55730"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/xtmim.com\/ja\/wp-json\/wp\/v2\/media\/55712"}],"wp:attachment":[{"href":"https:\/\/xtmim.com\/ja\/wp-json\/wp\/v2\/media?parent=55726"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/xtmim.com\/ja\/wp-json\/wp\/v2\/categories?post=55726"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/xtmim.com\/ja\/wp-json\/wp\/v2\/tags?post=55726"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}